I have a iPhone X (Sim Free) on T-Mobile with the latest official release of iOS 11. Recently, my text tone alert has stopped working. If I toggle the mute switch on and off (once) it will produce the text tone during testing. At some point, it stops working again. The phone was setup via backup from my other iPhone X (Verizon). Anyone run across this problem before? If so, any particular toggle I may have missed?